Device for sterilizing hollow thermoplastic articles by heat



INVENTOR.

1w? Arrmvfr P. KOLLSMAN DEVICE FOR STERILIZING HOLLOW THERMOPLASTIC ARTICLES BY HEAT Filed April 28, 1948 fI-I- Fig. 4

PAUL KoL/.sMA/v Fig. 3

. Patented Oct. 14, 1952 DEVICE FOR STERLILIZING HOLLOW THER- MOPLASTIC ARTICLES BY HEAT Paul Kollsman, New York, N. Y.

AAppualtnm April 2s, 194s, serial No. 23,826

v (ci. zi-ssl 3 Claims.

This invention relates to the art of sterilizing articles by heat and has particular application to the sterilizing of articles made of thermoplastic material which ordinarily do not lend themselves to treatment at ordinary sterilizing temperatures because of their inherent properties to soften and deform.

The bodies of hypodermic syringes, ampules, and receptacles for liquid or dry pharmaceutical materials are advantageously 'made from thermoplastic materials because of the ease with which such materials can be formed to precise dimensions within relatively close tolerances.

It is generally necessary to sterilize such articles after machining, molding. pressing, assembling or otherwise handling them. Sterilization by heat, which is generally accepted as one of the most efllcient methods of sterilizing, leads to diiiculties if applied to thermoplastics materials because of the inability of the material to withstand sterilizing temperatures for the necessary period of time without deformation due to the fact that the material assumes a plastic or semi-plastic state if heated.

The difficulty of sterilizing thermoplastic articles has been a major obstacle to a. more extensive use of thermoplastic materials for the aforementioned purposes in spite of the many advantages which thermoplastic materials offer in other respects over more conventional materials such as metal and glass. The invention provides an apparatus for heat sterilizing hollow articles, particularly hypodermic syringes, made from thermoplastic materials. According to the invention, the hollow article to be sterilized is conned or supported throughout the heating period in such a way that it will not warp, sag, or collapse and that after sterilization it has the precise dimensions which it is intended to have. More specically, this is accomplished by urging the hollow article against a coniining surface of appropriate dimensions by application of uid pressure in such a waythat the walls of the article itself constitute a form of membrane on which the pressure acts. According to the invention the article is acted upon by differential pressure applied to opposite sides of the wall of the article and it is further acted upon by a rigid, form constraining surface on one side. My co-pending application, Serial No. 23,825, filed April 28,' 1948, discloses and claims an arrangement in which the article is held between two rom constraining members.

The invention thus makes it possible to subject an article of a thermoplastic material which or- 2 dinarily begins to deform materially at temperatures of approximately degrees centigrade to sterilizing temperatures of the order of degrees centigrade without impairment or sacrice of the accuracy of its shape.

'Ihe various objects, features and advantages of the invention will appear more fully from the detailed description which follows accompanied by drawings showing for the purpose of illustration preferred embodiments of the invention. The invention also consists in certain new and original features of construction and combination oi' elements hereinafter set forth and claimed.

Although the characteristic features of the invention which are believed to be novel will be particularly pointed out in the claims appended hereto; the invention itself, its objects and advantages and the manner in which it may be carried out may be better understood by referring to the following description taken in connection with the accompanying drawings forming a part of it in which:

Figure 1 is a sectional side view of an article supporting and constraining device for use in sterilizing thermoplastic articles under heat and pressure;

Figure 2 is a side view, partly in section, of an apparatus for heat sterilizing thermoplastic articles;

Figure 3 is a sectional side view of a device for sterilizing liquid filled thermoplastic receptacles; and

Figure 4 is a sectional side view of an article supporting and constraining device of modied form.

In the following description and in the claims, various details will be identified by specific names for convenience. The names, however, are intended to be as generic in their application as the art will permit. Corresponding reference charac- .Y

ters refer to corresponding parts in the several gures of the drawings.

In the drawings accompanying, and forming part of, this speciilcation, certain specific disclosure of the invention is made for the purpose of explanation of broader aspects of the invention, but it is understood that the details may be modied in various respects without departure from the principles of the invention, and that the invention may be applied to other structures than the ones shown.

The device shown in Figure 1 comprises a coniining outer member or shell, Il having a flange l2 resting in an aperture I3 of a hollow casing I4. The flange l2 of theouter member Il includes a sealing ring or gasket Il resting inap. annular groove Il to provide a seal against which the flange il rests of a thermoplastic element -Il about to be sterilized. The illustrated element the flange Il of the thermoplastic syringe barrel Il and aids in supporting the top portion of the syringe barrel. Its weight tends to urge the barrel into contact with the seals Il and 2i.

The device shown in Figure 1 may be used as follows:

The hollow syringe barrel It of thermoplastic material which is intended to be sterilized by heat is first inserted intn the confining shell Il into which it fits with preferably a slight amount of play. The plug 2l is then placed on the barrel urging the flange l1 of the syringe barrel into contact with the gasket il and the front portion of the syringe barrel into contact with the seal 2|. The air pressure in the casing I4 is then reduced causing the syringe barrel to rest tightly against the seals il and 2|, respectively.

Subsequent application of sterilizing heat causes the thermoplastic material to assume a plastic or semi-plastic state. The pressure difierence between the outside and the inside oi the casing I4 causes the outer walls oi' the syringe to rest tightly against the contacting inner surface of the supporting shell Il whereby the syringe barrel is protected against deformation, warping or collapsing of its walls. During the heating, the barrel of the syringe also expands at a rate greater than the rate ot expansion of its conilning shell Il. The fluid pressure acting on the inside wall of the syringe body together with the forces caused by the thermal expansion urge the outer walls ci' the barrel against the inner surface of the supporting shell with a force sumcient to correct minor inaccuracies in the shape of the barrel.

After a sumcient period of time has elapsed, the device is permitted to cool. 'I'his causes the syringe barrel to contract slightly and at a rate greater than the rate of contraction ci the walls of the outer shell Il. This causes the syringe barrel to shrink slightly so that after equalization or pressure the sterile barrel may be removed from the shell.

The sterilizing device illustrated in Figure 2 comprises an autoclave Il having a removable cover or door Il. The autoclave may be heated by a. heating' unit 21 associated with a chamber or boiler portion 2l containing a charge 2t of water or other suitable liquid. The chamber 2t communicates with the interior of the autoclave through passages 2l whereby steam may be admitted into the interior of the autoclave for the purpose of heating the contents of the autoclave and furnishing the desired pressure.

The autoclave contains a casing I4 supporting a plurality of confining shells for syringe barrels or other hollow articles to be sterilized. A duct 3| leads from the interior of the casing I4 through the wall of the autoclave to a. pump I2 or other suitable source of vacuum in order to reduce the pressure inside the casing i4. Suitable indicators It and may be provided for observing temperature and pressure conditions inv side the autoclave.

The device shown in Figure 3 is particularly designed for sterilizing hollow receptacles containing a charge of liquid. The receptacles Il are supported in outer shells Il having an interior supporting surface t1 and communicating with the interior ci.' a chamber I4 through vent apertures 2l. In the form of device shown in Figure" 3. the liquid charge Il contained in the receptacle 'expands and provides internal vapor pressure during heating of the device to sterilizing temperatures for urging the walls of the receptacles against the supporting walls 31 of the shell. Simultaneously, the interior ot the chamber i4 may be evacuated in order to increase the force with which the walls of the receptacles are urged against the supporting surfaces surrounding them. A cover member 4| may be employed for supporting the bottom surface 4i of the receptacles.

The device illustrated in Figure 4 comprises an inner supporting member or post 42 which is threaded intoawall oracasing i4 at 4I.The post 42 has an air passage 44 therethrough through which air may be withdrawn or compressed air be applied. A restricted passage portion 45 limits the rate of ow through the passage 44. The post 42 is adapted to support the hollow barrel 4I of a hypodermic syringe of thermoplastic material which is to be sterilized. The bore 41 in the barrel into which a needle assembly may later be inserted is closed during the sterilizing process by a seal or stopper 48. A further seal or gasket 49 in the casing I4' seals the flange portion Il of the syringe barrel with respect to the casing I4'.

In the use of the device. air is ilrst withdrawn from the interior of the casing I4', whereby the flange portion Il of the barrel seats tightly against the gasket 4t. Heat is then applied for the purpose of sterilizing the barrel 4t. The heat causes the barrel to soften, but distortion or co1- lapse of the barrel is prevented by the post 42 against which the walls of the barrel are pressed by external pressure.

After sterilization the vacuum in the casing i4 is relieved. Air under pressure may then be applied to the interior or the casing I4' forcing the barrel 4t of! the post. The capillary passage 45 prevents escape of large amounts of air after the seal at 4! is broken or the barrel entirely removed from its support. A stop ll may be provided for the purpose of limiting the movement of the barrel under action ot the pressure.

The invention thus provides a simple and emcient device for heat sterilizing hollow articles of thermoplastic material which, by reason of their heat deformability present problems in sterilizing.

Obviously, the present invention is not restricted to the specific embodiments herein shown and described, but may, with equal benetlt, be applied or adapted to other forms of thermoplastic parts. Also the construction or the device may be modified without departing from the spirit and the essence of the present invention.

What is claimed is:

l. A device for sterilizing hollow elements of hypodermic syringes, said elements being of substantially cylindrical shape and having an open ended ange at one end and an apertured end wall at the other end, said elements being made of thermoplastic material assuming a plastic state at sterilizing temperatures, the device comprising a chamber; means for heating the interior of said chamber; a rigid post mounted inside said chamber, said post having a cylindrical outside surface thereon and a shoulder extending substantially normal to said cylindrical surface at the base of said post; a sealing ring in said shoulder about said cylindrical surface for sealing the ange of said hollow syringe element with respect to said surface, said post having a passage therethrough. one end of said passage terminating at said outside surface of the post,`

and a source of a pressure, the other end of said passage being in communication with said source of pressure.

2. A device for sterilizing hollow elements of hypodermic syringes, said elements being of substantially cylindrical shape and having an openended flange at one end and an apertured end wall at the other end, said elements being made of thermoplastic material assuming a plastic state at sterilizing temperatures, the device comprising. a chamber; means for heating the interior of said chamber; a rigid hollow member mounted inside said chamber.. said member having a molding surface thereon including a cylindrical surface portion said member further including a shoulder surface extending substantially at right angles from said cylindrical surface for supporting the flange of said element; a sealing ring recessed in said shoulder surface for sealing said flange with respect to said shoulder surface, said member further having a passage therethrough, one end of said passage terminating at said molding surface at a point most remote from the sealing ring; and a source of pressure lower than the pressure in said chamber, the other end of said passage being in communication with said source of pressure.

3. A device for sterllizing hollow elements of hypodermic syringes. said elements being of sub-I stantially cylindrical shape and having an openended ange at one end and an apertured end wall at the other end, said elements being made of thermoplastic material assuming a plastic state at sterilizing temperatures, the device comprising, a chamber; means for heating the interior of said chamber; a rigid substantially cup shaped member mounted inside said chamber, said member having molding surface thereon including an interior; cylindrical surface'portion, said member further including a shoulder surface extending substantially at right angles from said surface portion for supporting the flange of said element; a sealing, ring recessed in said shoulder surface for sealing said flange with respect to said shoulder surface; sealing means at the bottom of the cup shaped member for engaging and sealing the aperture in the end wall of said element. said member having a passage therethrough, one end of said passage terminating at said surface; at a point most remote from said sealing ring; and a source of pressure lower than the pressure in said chamber. the other end of said passage being in communication with said source of pressure.

PAUL KOLLSMAN.

REFERENCES CITED The following references are of record in the file of this patent:

- UNITED STATES PATENTS 

1. A DEVICE FOR STERILIZING HOLLOW ELEMENTS OF HYPODERMIC SYRINGES, SAID ELEMENTS BEING OF SUBSTANTIALY CYLINDRICAL SHAPE AND HAVING AN OPEN ENDED FLANGE AT ONE END AND AN APERTURED END WALL AT THE OTHER END, SAID ELEMENTS BEING MADE OF THERMOPLASTIC MATERIAL ASSUMING A PLASTIC STATE AT STERILIZING TEMPERATURES, THE DEVICE COMPRISING A CHAMBER; MEANS FOR HEATING THE INTERIOR OF SAID CHAMBER; A RIGID POST MOUNTED INSIDE SAID CHAMBER, SAID POST HAVING A CYLINDRICAL OUTSIDE SURFACE THEREON AND A SHOULDER EXTENDING SUBSTANTIALLY NORMAL TO SAID CYLINDRICAL SURFACE AT THE BASE OF SAID POST; A SEALING RING IN SAID SHOULDER ABOUT SAID CYLINDRICAL SURFACE FOR SEALING THE FLANGE OF SAID HOLLOW SYRINGE ELEMENT WITH RESPECT TO SAID SURFACE, SAID POST HAVING A PASSAGE THERETHROUGH, ONE END OF SAID PASSAGE TERMINATING AT SAID OUTSIDE SURFACE OF THE POST, AND A SOURCE OF A PRESSURE, THE OTHER END OF SAID PASSAGE BEING IN COMMUNICATION WITH SAID SOURCE OF PRESSURE. 